Porous systems (e.g., micropores or nanopores) in living organisms have evolved to extract fluids, vapors, and solids from soil, air, and ocean, sort them among internal compartments to control buoyancy, pressure, body patterning, sensing and metabolic cascades, and eliminate wastes, toxins, and pathogens.
In synthetic systems, a single system capable of complex multiphase selectivity and control has not been achieved, and fouling is nearly inevitable. Currently, many synthetic pore designs rely on static gating by precisely tailored chemistry, geometries, molecular fitting, and/or layering. To make transport responsive and controllable, active gates are designed to open and close the pores: polymers lining the pathway extend and recoil, hydrogel plugs swell and contract, “ball and chain” or “plunger” elements enter and exit, or elastomeric lids flex up and down. Yet for most systems, the need to balance surface chemistry and size requirements makes it difficult to differentially tune the behavior of multiple substances at once, and highly specific molecular pathways are observed only for pure liquid. The material requirements of responsive gates can further constrain options, and, for any nano/microscale transport, fouling is a universal problem that imposes another set of size and chemical considerations.
FIG. 30 shows a conventional pore (e.g., nanopore or micropore, which is significantly larger than molecular scale) in a solid material.
In such conventional pore systems, gas will flow through passively (i.e., the threshold pressure for gas (Pthreshold(gas)) is zero) regardless of shape and surface chemistry (see left of FIG. 30). In other words, transport of gases (left) is uncontrolled and can occur even at zero differential pressure. As used in the present disclosure, the “pressure” discussed herein refers to the pressure differential across the pore systems as compared to the pressure of the environment. For example, if operating under atmospheric conditions, zero pressure means that no additional differential positive or negative pressure is applied to the system, but the system is operating under atmospheric conditions.
Moreover, in conventional pore systems, liquid will deform and enter the pore as dictated by the balance of surface interactions, geometry, surface tension, and pressure (see right of FIG. 30). Specifically, liquids will enter and pass through the pore at an absolute threshold pressure that is greater than zero (i.e., |Pthreshold(liquid)|>0).
Moreover, while the liquid is flowing and even after the pressure is removed and the flow stops, some residual amounts of the liquid is shown to stick onto the pore surface and the system is prone to fouling.